A
perinatologist performed an amniocentesis on Linda after the first ultrasound
at 18 weeks. The doctor stuck a needle into her uterus to remove a vial's
worth of amniotic fluid. From this, they could culture some of the fetal
cells and examine the critter's genetics. The results were good: all
23 pairs of chromosomes were present and accounted for. The tests showed
no evidence of disorders such as Down's Syndrome, which involves the
baby having a third chromosome 21. (Eerie coincidence -- the last name
of the doctor who performed the amniocentesis was Downs.)